1. Field of the Invention
The present invention relates to a torque converter which is incorporated in a transmitting system mainly in an automobile, a motorcycle or the like and which includes a pump impeller connected to an input shaft, and a turbine impeller which is opposed to the pump impeller and to which a turbine shaft is connected.
2. Description of the Related Art
Such a torque converter is widely known, for example, as disclosed in Japanese Patent Application Laid-open No. 11-230303.
In such a known torque converter, when a back load is applied to the turbine shaft, a slipping occurs between the turbine impeller and the pump impeller. For this reason, it is impossible to provide a large engine brake effect such as when a manual transmission is used.
Accordingly, it is an object of the present invention to provide a torque converter of a high durability, which is designed so that a slipping is prevented from occurring between a turbine impeller and a pump impeller upon application of the back load to a turbine shaft, thereby providing a good engine brake effect.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a torque converter comprising a pump impeller connected to an input shaft, and a turbine impeller which is opposed to the pump impeller and to which a turbine shaft is connected, wherein the torque converter further includes a radial bearing and a one-way clutch, which are disposed coaxially adjacent to each other between a boss of a side-cover integrally connected to the pump impeller to cover the turbine impeller and the turbine shaft extending through the boss and connected to the turbine impeller, the radial bearing serving to retain the boss and the turbine shaft concentrically, and the one-way clutch connecting the turbine shaft and the radial bearing to each other when a back load is applied to the turbine shaft.
With the arrangement of the first feature, when the back load is transmitted from a drive gear to the turbine shaft during deceleration of a vehicle, the one-way clutch connects the turbine shaft and the side-cover to each other, so that the back gear is transmitted from the turbine shaft directly to the side-cover and further from the pump impeller to a crankshaft. Therefore, a slipping cannot occur between the turbine impeller and the pump impeller, and a good engine brake effect can be provided. Moreover, the radial ball bearing adjacent to the one-way clutch is interposed between the turbine shaft and the side-cover to ensure the concentricity of the turbine shaft and the side-cover with each other. Therefore, a load received by the clutch element of the one-way clutch such as a sprag between the turbine shaft and the side-cover is equalized, whereby the durability of the clutch can be enhanced.
According to a second aspect and feature of the present invention, in addition to the first feature, the radial bearing is axially non-movably mounted on the boss of the side-cover, and a boss of the pump impeller is secured to the input shaft, so that a thrust load applied to an output gear which is connected to an outer end of the turbine shaft in a direction toward the turbine impeller is applied to the radial bearing.
With the arrangement of the second feature, during transmission of the torque, a thrust load generated on the output gear in the direction toward the turbine impeller is borne on the input shaft from the radial bearing through the side-cover and the pump impeller each having a relatively high rigidity. Therefore, it is possible to avoid the bearing of the thrust load on the turbine impeller and the stator impeller to enhance the durability of them.
According to a third aspect and feature of the present invention, in addition to the first or second feature, the boss of the pump impeller is secured to the input shaft, and the radial bearing has an outer race which is axially non-movably mounted to the boss of the side-cover, and an inner race which is axially non-movably retained on the turbine shaft.
With the arrangement of the third feature, an assembly of the torque converter can be formed by cooperation of the bearing and the output gear with each other before assembling of the torque converter to the crankshaft. Therefore, during assembling of the torque converter to the crankshaft, the boss of the pump impeller is secured to the input shaft. Therefore, the entire torque converter can be axially positioned and moreover, during transmission of the torque, the thrust load applied to the output gear is borne on the input shaft from the radial bearing through the side-cover and the pump impeller each having a relatively high rigidity, irrespective of the direction of the thrust load. Therefore, it is possible to avoid the bearing of the thrust load on the turbine impeller and the stator impeller to enhance the durability of them.
According to a fourth aspect and feature of the present invention, in addition to any of the first, second and third features, a seal means is provided between the turbine shaft and the side-cover at a location displaced from the radial bearing and the one-way clutch in a direction opposite to the turbine impeller for sealing the turbine shaft and the side-cover from each other.
With the arrangement of the fourth feature, the radial bearing and the one-way clutch can be lubricated by oil filling the inside of the side-cover of the torque converter, and the oil can be prevented from being leaked to the outside through between the turbine shaft and the side-cover.
According to a fifth aspect and feature of the present invention, in addition to any of the first, second and third features, the radial bearing is formed with a seal and disposed on the side opposite of the one-way clutch to the turbine impeller.
With the arrangement of the fifth feature, the one-way clutch can be lubricated by oil filling the inside of the side-cover of the torque converter, and the oil can be prevented from being leaked to the outside by the radial bearing.
According to a sixth aspect and feature of the present invention, in addition to the fifth feature, the output gear fixedly mounted at the outer end of the turbine shaft is opposed to an outer end of the boss of the side-cover, and a seal ring is slidably fitted to an inner peripheral surface of the outer end of the boss of the side-cover and come into close contact with a side face of the output gear upon reception of the pressure of the oil passed through the bearing.
With the arrangement of the sixth feature, when the seal of the radial bearing is damaged to permit the oil within the side-cover to be passed through the bearing, the pressure of the oil causes the seal ring to be forced against a bottom surface of an annular recess in the output gear, whereby the oil can be prevented from being leaked to the outside. Moreover, in a normal state in which the seal of the ball bearing has no damage, the pressure urging the seal ring against the output gear is not generated. Therefore, no frictional resistance is produced between the seal ring and the output gear and hence, it is possible to prevent a frictional loss of power due to the seal ring.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings.